fix(reasoning): preserve investigation ownership across selection and question rejection

lib/graph/apply-proposal.js

@@ -2871,6 +2871,9 @@ function reseatSelectionAfterQuestionRejection({
     : { status: "none", nodeId: null };
 }
 
+const QUESTION_FORMULATION_REJECTION_NO_QUESTION_REASON =
+  "The selected investigation target remains active, but its current graph-backed question formulation was rejected as too complex.";
+
 export function determineGraphBackedQuestion({ situationGraph }) {
   const graphSnapshot = cloneJsonSafe(situationGraph);
   let updatedSituationGraph = cloneJsonSafe(situationGraph);
@@ -2937,15 +2940,12 @@ export function determineGraphBackedQuestion({ situationGraph }) {
     initialQuestionRejected &&
     deterministicSelection?.status === "selected"
   ) {
-    deterministicSelection = reseatSelectionAfterQuestionRejection({
-      graph: updatedSituationGraph,
-      deterministicSelection,
-      excludedNodeIds: [deterministicSelection.nodeId],
-    });
-    questionResult = buildSelectedQuestionResult({
-      updatedSituationGraph,
-      deterministicSelection,
-    });
+    questionResult = {
+      ...questionResult,
+      selectedQuestion: null,
+      questionSuppressedReason:
+        QUESTION_FORMULATION_REJECTION_NO_QUESTION_REASON,
+    };
   }
 
   if (
@@ -2971,14 +2971,15 @@ export function determineGraphBackedQuestion({ situationGraph }) {
       ? questionResult.selectedQuestion?.questionSuppressedReason ||
         questionResult.selectedQuestion?.reason ||
         "Eligible unresolved candidates remain tied after initial graph-backed selection."
-      : (updatedSituationGraph.nodes || []).some(
+      : questionResult.questionSuppressedReason ||
+          ((updatedSituationGraph.nodes || []).some(
             (node) =>
               node.kind === "unknown" &&
               !["resolved", "contradicted"].includes(node.status) &&
               !(updatedSituationGraph.resolvedNodeIds || []).includes(node.id),
           )
-        ? "Compatible unresolved candidates remain, but none produced a valid graph-backed question."
-        : "No unresolved unknown candidates remain after initial graph construction.";
+            ? "Compatible unresolved candidates remain, but none produced a valid graph-backed question."
+            : "No unresolved unknown candidates remain after initial graph construction.");
 
   return {
     success: true,